Pump run time question

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scuba
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My Pool: 30k gal free form diving, pebble tec, salt water
Location: Texas

Pump run time question

Postby scuba » Wed 20 Jul, 2011 13:10

I have a IntelliFlo VS+SVRS pump and run it 8 hours/day at 3050RPM. Crude flow rate calculation shows 150GPM at this RPM so it will take 3.3 hours to turn over 100% water (30k Gal).

Question is, can I cut down the pump run time to 4 hour per day and have same clear water? Running the SWGC at 100% should give me the same Cl it generates during 8 hours at 50%.

* FC: 4
* TC:
* pH: 7.8
* TA: 120
* CH: 250
* CYA: 100

* My pool: in ground, 30K Gal, PebbleTec
* Pool chemicals: the chemicals you use for pool maintenance (chlorine, bromine, ...)
* My pump & filter: Pentair 3HP
* Other info: 93F, normal, Texas summer heat, sun on pool


czechmate
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My Pool: 16 x 32 gunite21000 gal., Diamond Brite Blue, Swimquip XL pump, DE36
Location: Texas

Pump run time question

Postby czechmate » Wed 20 Jul, 2011 14:36

You should first lower your TA to 100ppm and your PH to 7.6 to protect your plaster.
It is very important an pretty easy. Your CSI is creeping up.
I also hear that splitting the pump run in 2hr runs is more effective than a sustained run.
scuba
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My Pool: 30k gal free form diving, pebble tec, salt water
Location: Texas

Pump run time question

Postby scuba » Fri 22 Jul, 2011 20:48

I can lower TA to 100ppm by adding a gal of acid. Just curious though, the recommended TA range is 80-150ppm, mine is 120ppm so theoretically well within range/spec. Do I really need to go to a 100ppm? Water is crystal clear, plaster is spotless.

I did switch to two 3 hour runs, 12 hours apart. Should give me 2 turns of water over a 24 hour period. Keeping an eye on any changes.

Another interesting variable that I read about is the aeration, I have a waterfall and a spa fountain that run with the pump. So theoretically if I turn these features off the ph would be more manageable? currently it creeps up to ~8 on a monthly basis. Thanks a bunch for your help.
czechmate
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My Pool: 16 x 32 gunite21000 gal., Diamond Brite Blue, Swimquip XL pump, DE36
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Pump run time question

Postby czechmate » Sat 23 Jul, 2011 08:50

TA level plays an important role in protection of your plaster due to its effect on CSI.
I always consider it along with the PH level to keep CSI neutral in wide range of changing temperatures.
It is the easy and quick way.
There is still a lot of pool owners out there that are pretty scared of algae, but forget about protection of their plaster.
Corosion of plaster can start without warning and go undetected for couple of months, specially in winter. Nice clean blue water often gives people false feeling of "all is OK" status.
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mas985
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Pump run time question

Postby mas985 » Sun 24 Jul, 2011 18:48

scuba wrote:I have a IntelliFlo VS+SVRS pump and run it 8 hours/day at 3050RPM. Crude flow rate calculation shows 150GPM at this RPM so it will take 3.3 hours to turn over 100% water (30k Gal).

Question is, can I cut down the pump run time to 4 hour per day and have same clear water? Running the SWGC at 100% should give me the same Cl it generates during 8 hours at 50%.


Why not cut the speed down instead?

But first, there is no way you are getting anywhere close to 150 GPM on typical pool plumbing. That is the runout flow rate. On 2" plumbing, you could expect around 90 GPM @ 3050 RPM. But unless you really need that high of a flow rate for something specific, you could save a lot of energy costs running the pump at 1000 RPM instead. Flow rate would be about 30 GPM and with a turnover of 17 hours. 1 turnover @ 30 GPM will cost about 80% less than 1 turnover at 3050 RPM. In fact, if you wanted to you could set the speed to 700 RPM and never turn it off. The flow rate would be around 21 GPM for a 24 hour turnover.
Mark
Hydraulics 101 ; Pump and Pool Spreadsheets ; Pump Ed 101
18'x36' 20k gallon plaster/gunite pool, 1/2 HP 2sp pump, Aqualogic PS8 SWCG, 420 sq-ft Cartridge Filter, Solar Panels, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater
scuba
Pool Newbie
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Posts: 8
Joined: Sun 05 Jun, 2011 16:04
My Pool: 30k gal free form diving, pebble tec, salt water
Location: Texas

Pump run time question

Postby scuba » Mon 25 Jul, 2011 19:20

You 2 have given me super tips, thanks a bunch czechmate and mas985. I am lowering the TA to 100 and ph to 7.6. czechmate, I totally missed the pressure drop factor! At 3050rpm the water features run pretty cool, at 1000rpm they die out so better to turn them off altogether. However at 2400rpm I still get the water features to operate fine and do cut the wattage in half (~1000watts instead of ~2000watts at 3050rpm). So running 8 hours split in 2 sets of 4 hours still gets me about 1 turnover. Will run for a month and see.
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mas985
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Pump run time question

Postby mas985 » Tue 26 Jul, 2011 10:43

Water features will tend to raise PH not to mention increase evaporation and that works great for lowering TA with acid dosing cycles (add acid->raise PH->add acid...) but after you get the TA down, you might consider shutting off the water features and lowering the RPM to save money on the pump energy costs.
Mark
Hydraulics 101 ; Pump and Pool Spreadsheets ; Pump Ed 101
18'x36' 20k gallon plaster/gunite pool, 1/2 HP 2sp pump, Aqualogic PS8 SWCG, 420 sq-ft Cartridge Filter, Solar Panels, 6 jet spa, 1 HP jet pump, 400k BTU NG Heater
cpo2go
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Pump run time question

Postby cpo2go » Fri 29 Jul, 2011 23:54

Just one quart of acid will put, both your TA and pH in the right place. Consider that I'm basing that on your last readings. You should test again before adding anything.
You're correct, though, 120 is fine. With your CYA so high, it makes your actual TA number lower. 1/3 of of your CYA contributes to your TA so your actual TA is 90ppm,
My bigger concern is your CYA being 100. The only way to lower this quickly is to drain half your water and re-fill. This would make your CYA 50ppm which is closer to where it should be. 30ppm is perfect. A good range is 25-40ppm. 50 is the maximum at which I ever keep a pool. It's not a big deal to lower it quickly, however. It will slowly go down on it's own. Keeping it at that high level will result in staining and chlorine lock. If you're using chlorine tabs, switch to liquid chlorine until next Summer and you should be fine.
Also you mention that you use chlorine and bromine. In a pool as hot as yours, I don't have a huge problem with you using bromine for maintaining a residual in the water and shocking with chlorine but otherwise, you don't need both. If you are doing what I just mentioned, granular chlorine (dichlor) would be a good choice because it will also lower your alkalinity (again, not a concern at this time) and help keep your pH down. However, until you get your CYA down, stick with liquid chlorine. Dichlor also contributes CYA to your water.
For your pump runtime, slow the pump down to about half of what you're doing now, 1500RPM, and run the pump longer. Those pumps are designed to run at super high efficiency by adjusting the speed down and run time up. A great benefit to this is not only that you'll save on electrical use, but that it allows your cleaner, if you have one, to run more hours resulting in a cleaner pool. :thumbup:
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